Climate Science Glossary

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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Scientific skepticism is healthy. Scientists should always challenge themselves to improve their understanding. Yet this isn't what happens with climate change denial. Skeptics vigorously criticise any evidence that supports man-made global warming and yet embrace any argument, op-ed, blog or study that purports to refute global warming. This website gets skeptical about global warming skepticism. Do their arguments have any scientific basis? What does the peer reviewed scientific literature say?

Editor's Pick

A poplar tree farm in Oregon is a fast-growing bioenergy source.

On a sunny day this past October, three dozen people file into a modest, mint-green classroom at Montana State University (MSU) in Bozeman to glimpse a vision of the future. Some are scientists, but most are people with some connection to the land: extension agents who work with farmers, and environmentalists representing organizations such as The Nature Conservancy. They all know that climate change will reshape the region in the coming decades, but that's not what they've come to discuss. They are here to talk about the equally profound impacts of trying to stop it.

Paul Stoy, an ecologist at MSU, paces in front of whiteboards in a powder blue shirt and jeans as he describes how a landscape already dominated by agriculture could be transformed yet again by a different green revolution: vast plantations of crops, sown to sop up carbon dioxide (CO2) from the sky. "We have this new energy economy that's necessary to avoid dangerous climate change, but how is that going to look on the ground?" he asks.

In 2015, the Paris climate agreement established a goal of limiting global warming to "well below" 2°C. In the most recent report of the Intergovernmental Panel on Climate Change, researchers surveyed possible road maps for reaching that goal and found something unsettling. In most model scenarios, simply cutting emissions isn't enough. To limit warming, humanity also needs negative emissions technologies (NETs) that, by the end of the century, would remove more CO2from the atmosphere than humans emit. The technologies would buy time for society to rein in carbon emissions, says Naomi Vaughan, a climate change scientist at the University of East Anglia in Norwich, U.K. "They allow you to emit more CO2 and take it back at a later date."

Posted on 16 February 2018 by Ari Jokimäki

John's new paper

"Misinformation can have significant societal consequences. For example, misinformation about climate change has confused the public and stalled support for mitigation policies. When people lack the expertise and skill to evaluate the science behind a claim, they typically rely on heuristics such as substituting judgment about something complex (i.e. climate science) with judgment about something simple (i.e. the character of people who speak about climate science) and are therefore vulnerable to misleading information. Inoculation theory offers one approach to effectively neutralize the influence of misinformation. Typically, inoculations convey resistance by providing people with information that counters misinformation. In contrast, we propose inoculating against misinformation by explaining the fallacious reasoning within misleading denialist claims. We offer a strategy based on critical thinking methods to analyse and detect poor reasoning within denialist claims. This strategy includes detailing argument structure, determining the truth of the premises, and checking for validity, hidden premises, or ambiguous language. Focusing on argument structure also facilitates the identification of reasoning fallacies by locating them in the reasoning process. Because this reason-based form of inoculation is based on general critical thinking methods, it offers the distinct advantage of being accessible to those who lack expertise in climate science. We applied this approach to 42 common denialist claims and find that they all demonstrate fallacious reasoning and fail to refute the scientific consensus regarding anthropogenic global warming. This comprehensive deconstruction and refutation of the most common denialist claims about climate change is designed to act as a resource for communicators and educators who teach climate science and/or critical thinking."

Climate change mitigation

"Even though coal consumption has recently declined and plans to build new coal-fired capacities have been shelved, constructing all these planned coal-fired power plants would endanger national and international climate targets. Plans to build new coal-fired power capacity would likely undermine the credibility of some countries’ (Intended) Nationally Determined Contributions submitted to the UNFCCC. If all the coal-fired power plants that are currently planned were built, the carbon budget for reaching the 2 °C temperature target would nearly be depleted. Propositions about ‘coal’s terminal decline’ may thereby be premature."

Posted on 13 February 2018 by Guest Author

When I was a brand-new PhD student, full of innocence and optimism, I loved solving bugs. I loved the challenge of it and the rush I felt when I succeeded. I knew that if I threw all of my energy at a bug, I could solve it in two days, three days tops. I was full of confidence and hope. I had absolutely no idea what I was in for.

Now I am in the final days of my PhD, slightly jaded and a bit cynical, and I still love solving bugs. I love slowly untangling the long chain of cause and effect that is making my model do something weird. I love methodically ruling out possible sources of the problem until I eventually have a breakthrough. I am still full of confidence and hope. But it’s been a long road for me to come around full circle like this.

As part of my PhD, I took a long journey into the world of model coupling. This basically consisted of taking an ocean model and a sea ice model and bashing them together until they got along. The coupling code had already been written by the Norwegian Meteorological Institute for Arctic domains, but it was my job to adapt the model for an Antarctic domain with ice shelf cavities, and to help the master development team find and fix any problems in their beta code. The goal was to develop a model configuration that was sufficiently realistic for published simulations, to help us understand processes on the Antarctic continental shelf and in ice shelf cavities. Spoiler alert, I succeeded. (Paper #1!Paper #2!) But this outcome was far from obvious for most of my PhD. I spent about two and a half years gripped by the fear that my model would never be good enough, that I would never have any publishable results, that my entire PhD would be a failure, etc., etc. My wonderful supervisor insisted that she had absolute confidence in my success at every step along the way. I was afraid to believe her.

Research indicates that natural causes do not explain most observed warming, especially warming since the mid-20th century. Rather, it is extremely likely that human activities have been the dominant cause of that warming.

To support this statement, the EPA referenced the latest IPCC report. The IPCC concluded with 95% confidence that humans are the main cause of global warming since 1950, with a best estimate that humans are responsible for all of the global warming during that time. That’s what the scientific research has overwhelmingly concluded:

The percentage of human contribution to global warming over the past 50-65 years from various peer-reviewed studies. Illustration: Dana Nuccitelli and John Cook

Posted on 11 February 2018 by John Hartz

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Story of the Week...

Keeping the world below 2°C of warming needs tech we don’t have

Reforesting would help, but we're still deforesting. Photo: Mikko Muinonen

The analysis is well known to everyone who has paid even a little attention: the world hasn’t yet done enough to lessen the impacts of climate change. The last Intergovernmental Panel on Climate Change report included greenhouse gas emissions scenarios that could limit global warming to two degrees Celsius or less, but we’re not even close to a trajectory that would achieve any of them.

But there’s something about those two-degrees scenarios you may not know, which climate scientists have been talking a lot about recently. Those scenarios involved a substantial deployment of technologies to actively remove CO2 from the atmosphere. Without those technologies, we’re even further from sufficient emissions cuts.

That leaves us with a crucial question: can carbon dioxide removal techniques be scaled up to the necessary level in time? A new European Academies Science Advisory Council (EASAC) report—reviewed and endorsed by the national academies of more than two dozen countries—evaluates the outlook for carbon dioxide removal. And it’s not optimistic.

Posted on 10 February 2018 by John Hartz

Editor's Pick

Tesla is building a 'virtual power plant' using people's homes

South Australia is working with Tesla to install solar power systems on residents homes. Image: REUTERS/Mario Anzuoni

The state government of South Australia announced Sunday that it had struck a deal with Tesla to install as many as 50,000 solar-power systems on homes, at no cost to residents.

The system would include both solar panels and Tesla Powerwall batteries, and would become part of a decentralized electric grid managed by software. The system would be funded in part by revenues from electricity, which would not belong to the owners of the homes where the systems were installed.

A pilot version of the program has already begun, and the Australian Broadcasting Corporation spoke to one early recipient whose electric bills had declined substantially. One projection suggested energy bills for participating households would drop by 30%.

Posted on 9 February 2018 by Ari Jokimäki

Climate change impacts

"We calculated the ITCC of spring wheat in Wuchuan County as an example and identified warming and drying trends in Wuchuan County from 1961 to 2013, especially during the period from 1991 to 2013 (i.e., the period after mutation or the change period). Over the past 53 years, spring wheat yield increased with an average rate of 81.3 kg ha−1 dec−1. Over the change period, however, yield decreased with an average rate of 13.8 kg ha−1 dec−1 and the fluctuation range increased. The appropriate threshold for average temperature during the growth period of spring wheat was 11.4 °C, and the stressed thresholds were 8.2 and 14.6 °C. The appropriate threshold for precipitation during the growth period was 391.1 mm, and the stressed thresholds were 247.4 and 534.9 mm. During the period before mutation (i.e., the basic period), the average temperature was below the upper temperature threshold, and precipitation was 26.9 mm above the lower precipitation threshold. During the change period, the average temperature was 0.3 °C above the upper temperature threshold, and precipitation was 9.8 mm above the lower precipitation threshold."

Posted on 8 February 2018 by John Abraham

As humans continue to emit greenhouse gases like carbon dioxide, the world continues to warm. We see that warming everywhere – in the atmosphere, in the oceans, with rising sea levels, and melting ice. But while we know conclusively that humans are causing the warming, an equally important question is, “so what?” Really, we want to know the consequences of warming so that we can make informed decisions about what to do about it. We really have only three choices: mitigate, adapt, or ignore and suffer the consequences.

A very new study was just published that helps answer this question of “so what?” The research was conducted by lead author Lorenzo Alfieri (European Commission – Joint Research Centre, Italy), Richard Betts (University of Exeter and Met Office, UK), and their colleagues.

In the study, the authors used what are called Impact Models to assess the risks of large-scale flooding. They focused their attention on Europe partly because there is a lot of hydrological information there, flood reporting is easily available, and predictions of future climate there are plentiful. The authors compared estimates of flood risk in Europe from three recent case studies; their comparison incorporated changes to future climate, expected damage, and population that will be affected in the flooding zones.

I think of this as a three-part study. First, the authors obtained climate projections for Europe using state-of-the-art climate models. Next, they input the future climate into calculations that quantify flood risk and the impacts. Last, they compared the results that they obtained from their different damage calculation algorithms. The authors looked for areas where the calculations agreed or disagreed with each other. At the end of the day, they wanted to answer two key questions:

1. Is it possible to identify trends that are consistent among the models to help Europe prepare for changes to flood risk?

Over the past several years there have been a number of reports from some of these "converts" explaining how they changed their minds. This post looks at some of these accounts with the goal of discovering what led these people to change their minds. This is by no means an exhaustive list. If you know of other examples not seen here please add to the list in the comments section.

Two Scientists - "Total turnaround"

Scientists are naturally, and appropriately, skeptical. They ask questions about how the world works; and when they find answers they ask further questions about those answers, always striving to get to better explanations of the natural world. So it is no surprise that scientists would turn their skeptical eyes to anthropogenic climate change (AGW).

Kasra Hassani was a scientist working in microbiology and immunology who had a skeptical view of climate science. At first he thought there were more immediate problems facing humankind than climate change. For a time, he toyed with conspiracy theories about AGW (thanks to Michael Crichton's State of Fear), but more and more evidence for climate change forced him to face reality:

I created a list of every question and doubt I had about the physics, chemistry, biology, economics and politics of climate change, and I started reading. I took online courses. I listened to podcasts. Every myth in my head popped and floated away.

Hassani also said,

No singular bit of evidence unequivocally proved to me that humans were responsible for climate change, which makes sense if you're a science nut like me. Science works on multiple proofs. One experiment or piece of evidence supports a theory, it doesn’t prove anything.

Over time, as different researchers gather more evidence, a theory becomes refined and a more acceptable explanation for natural phenomena. It also took time because I was never astonished by a piece of evidence or a big news story; when you are in denial, evidence is unlikely to change your mind. On the contrary, it might persuade you to cover your ears and pretend you're not listening.

Hassani realized that denial was the easier answer. The real effort was in recognizing his own biases, and seeing that his own strong-held beliefs and stubbornness went beyond a healthy skepticism:

Posted on 6 February 2018 by dana1981, John Cook

Climate myths are often contradictory – it’s not warming, though it’s warming because of the sun, and really it’s all just an ocean cycle – but they all seem to share one thing in common: logical fallacies and reasoning errors.

John Cook, Peter Ellerton, and David Kinkead have just published a paper in Environmental Research Letters in which they examined 42 common climate myths and found that every single one demonstrates fallacious reasoning. For example, the authors made a video breaking down the logical flaws in the myth ‘climate changed naturally in the past so current climate change is natural.’

Video abstract for paper “Deconstructing climate misinformation to identify reasoning errors” published in Environmental Research Letters by John Cook, Peter Ellerton, and David Kinkead.

Despite the huge strides taken since the earliest climate models, there are some climatic processes that they do not simulate as accurately as scientists would like.Advances in knowledge and computing power mean models are constantly revised and improved. As models become ever more sophisticated, scientists can generate a more accurate representation of the climate around us.

But this is a never-ending quest for greater precision.

In the third article in our week-long climate modelling series, Carbon Brief asked a range of climate scientists what they think the main priorities are for improving climate models over the coming decade.

These are their responses, first as sample quotes, then, below, in full:

Story of the Week...

Why Climate Deniers Target Women

Harassment is no stranger to the reporters, researchers and policymakers who work on climate change, but it is particularly severe for the women in those fields.

Canadian environment minister Catherine McKenna was labeled “climate Barbie” by the right-wing political blog The Rebel Media. Kait Parker of the Weather Channel suffered attacks from Breitbart News, which dismissed her forceful and lucid explanation of climate science as an “argument from a pretty girl.” Emily Atkin, who covers climate and energy for The New Republic, also has endured sexist barbs from Breitbart, which said she had “kitty claws,” and Rush Limbaugh, who called her an “infobabe.” In similar fashion, climate scientist Katharine Hayhoe earned the moniker “climate babe” from Limbaugh.

Certainly, sexist attacks are not unique to climate science, journalism or advocacy, but research into public understanding of climate change reveals an important link between sexism and climate denial — support for the existing social hierarchy.

Posted on 3 February 2018 by John Hartz

Editor's Pick

Ice, fire, storms and heat: Climate change is now part of our everyday lives

While the West Coast was being inundated, on the other side of the Alps, there were fires. Photo: Iain McGregor/Stuff

Analysis: January 2018 was officially the hottest month ever recorded in New Zealand.

Niwa made the announcement on Friday afternoon, as communities on the West Coast were mopping up the mess created by a powerful storm that descended over eroding coasts; as some in Dunedin settled into their homes after a sweeping fire while others in low-lying parts of the city clear up after yet another flood; as it was snowing in Cromwell during the hottest summer in many years, after a month where the mean air temperature was 3C warmer than usual, based on the country's century-old seven-station record.

Earlier in the week, the news was filled with fan shortages, wildfires and mountains shedding rock because of a lack of snow; at its end, it was 14C in parts of central Otago, multiple areas near Christchurch were on fire, and homes throughout the South Island had been damaged by the sea. An ominous super blood moon part way through the week, whilst unrelated, summed up the vibe: unsettled, bordering on Biblical.

Posted on 2 February 2018 by Ari Jokimäki

Climate change

"The basic result was that even as the lower atmosphere gradually warms, the upper atmosphere rapidly cools. The simulations employed constant low solar activity conditions, to remove the effects of variable solar and geomagnetic activity. Global mean annual mean temperature increased at a rate of +0.2 K/decade at the surface and +0.4 K/decade in the upper troposphere, but decreased by about -1 K/decade in the stratosphere-mesosphere, and -2.8 K/decade in the thermosphere. Near the mesopause, temperature decreases were small compared to the interannual variation, so trends in that region are uncertain."

Posted on 1 February 2018 by dana1981

Donald Trump has decimated all presidential norms to such a degree that it’s now difficult to feel alarmed or outraged when he inevitably breaks another. It was difficult to raise an eyebrow when the story broke that Trump paid off a porn star to remain silent about their affair, which happened just after his third wife had given birth to his fifth child, because it’s Donald Trump – of course he did.

But that’s not okay. Donald Trump is the leader of the country most culpable for the existential threat that we’ve created by rapidly changing Earth’s climate. His administration is alone in the world in declaring that we need not worry about that existential threat. We need to hold him to account for his ignorance on this critically important issue and demand better.

Trump’s ignorant climate comments

Trump’s climate comments in the interview were so ridiculously misinformed that even late night comedians were able to debunk them:

They’re claims you might expect from a YouTube troll, not the leader of the country that produces some of the best climate science research and data in the world. It would be easy to laugh them off as Trump’s usual buffoonery, but he should be held to a presidential standard. So, to briefly debunk each of these myths:

Posted on 31 January 2018 by Guest Author

Damage from extreme weather events during 2017 racked up the biggest-ever bills for the U.S. Most of these events involved conditions that align intuitively with global warming: heat records, drought, wildfires, coastal flooding, hurricane damage and heavy rainfall.

Paradoxical, though, are possible ties between climate change and the recent spate of frigid weeks in eastern North America. A very new and “hot topic” in climate change research is the notion that rapid warming and wholesale melting of the Arctic may be playing a role in causing persistent cold spells.

A ‘dipole’ of abnormal temperatures

Weird and destructive weather was in the news almost constantly during 2017, and 2018 seems to be following the same script. Most U.S. Easterners shivered their way through the end of 2017 into the New Year, while Westerners longed for rain to dampen parched soils and extinguish wildfires. Blizzards have plagued the Eastern Seaboard – notably the “bomb cyclone” storm on Jan. 4, 2018 – while California’s Sierra Nevada stand nearly bare of snow.

A study in contrasts: Warming near Alaska and the Pacific Ocean are ‘ingredients’ to a weather pattern where cold air from the Arctic plunges deep into North America.NASA Earth Observatory, CC BY

Posted on 30 January 2018 by Zeke Hausfather

The climate data for 2017 is now in. In this article, Carbon Brief explains why last year proved to be so remarkable across the oceans, atmosphere, cryosphere and surface temperature of the planet.

A number of records for the Earth’s climate were set in 2017:

It was the warmest year on record for ocean heat content, which increased markedly between 2016 and 2017.

It was the second or third warmest year on record for surface temperature – depending on the dataset used – and the warmest year without the influence of an El Niño event.

It saw record lows in sea ice extent and volume in the Arctic both at the beginning and end of the year, though the minimum extent reached in September was only the eighth lowest on record.

It also saw record-low Antarctic sea ice for much of the year, though scientists are still working to determine the role of human activity in the region’s sea ice changes.

Warmest year on record in the oceans

More than 90% of the heat trapped by increasing greenhouse gas concentrations ends up going into the Earth’s oceans. While surface temperatures fluctuate a bit from year to year due to natural variability, ocean heat content increases much more smoothly and is, in many ways, a more reliable indicator of the warming of the Earth, albeit one with a shorter historical record.

The figures below shows ocean heat content for each year in the region of the ocean between the surface and 2,000 meters in depth (comprising the bulk of the world’s oceans), as well as a map of 2017 anomalies.

The upper figure shows changes in ocean heat content since 1958, while the lower map shows ocean heat content in 2017 relative to the average ocean heat content between 1981 and 2010, with red areas showing warmer ocean heat content than over the past few decades and blue areas showing cooler.

Change in global ocean heat content between the surface and 2000 meters of depth from 1958 to 2017 (top) and distribution of ocean heat content anomalies in 2017 (bottom). Figure from Cheng and Zhu (2018), using data from IAP-CAS.

Posted on 29 January 2018 by dana1981

Over the past decade, coal has been increasingly replaced by cheaper, cleaner energy sources. US coal power production has dropped by 44% (866 terawatt-hours [TWh]). It’s been replaced by natural gas (up 45%, or 400 TWh), renewables (up 260%, or 200 TWh), and increased efficiency (the US uses 9%, or 371 TWh less electricity than a decade ago).

Evolution of the American power grid mix since 1960. Illustration: Carbon Brief

In other words, of the 866 TWh of lost coal power production, 46% was picked up by natural gas, 43% by increased efficiency, and 23% by renewables.

Natural gas is an unstable ‘bridge fuel’

While the shift away from coal is a positive development in slowing global warming by cutting carbon pollution, as Joe Romm has detailed for Climate Progress, research indicates that shifting to natural gas squanders most of those gains. For example, a 2014 study published in Environmental Research Letters found that when natural gas production is abundant, it crowds out both coal and renewables, resulting in little if any climate benefit. Part of the problem is significant methane leakage from natural gas drilling.